Final answer:
An 18-month-old boy displaying frequent crying, difficulty soothing, and frequent waking during the night would be considered an example of infant distress.
Step-by-step explanation:
An 18-month-old boy displaying frequent crying, difficulty soothing, and frequent waking during the night would be considered an example of infant distress according to Thomas and Chess.
Infant distress is a normal developmental phase where infants experience emotional distress and manifestations of negative affect. It is a common occurrence during early childhood as children learn to regulate their emotions. Infants may cry frequently, have difficulty soothing themselves, and experience sleep disturbances.
This behavior is a part of infant development and can be attributed to factors such as hunger, discomfort, tiredness, teething, or a need for comfort or attention from a caregiver. It is important for parents and caregivers to provide a secure and nurturing environment while understanding that this phase is temporary and will pass as the child develops further.